In recent years, LEDs have come to be used frequently as light sources for illumination apparatuses. Methods for obtaining white light in the illumination apparatus using LEDs include, for example, a method using three kinds of LEDs, that is, a red LED, a blue LED, and a green LED, and a method utilizing a fluorescent material that converts excited light from a blue LED to emit yellow light. With respect to the light sources for illumination apparatuses, since white light having sufficient luminance is required, illumination apparatuses using a plurality of LED chips have been commercialized.
For one example of such an illumination apparatus, Japanese Patent Laying-Open No. 2003-152225 (Patent Document 1) discloses a light emitting device 101 as schematically shown in FIG. 14. Light emitting device 101 shown in FIG. 14 has a structure in which element storage units 103, each having a concave shape, are formed on a metal plate 102 made of aluminum, and a printed circuit board 104, which is an insulating glass epoxy substrate with a wiring unit 105 made of copper foil being placed thereon, is formed between the element storage units. Moreover, in the example shown in FIG. 14, a light emitting element 106, placed (disposed) on each element storage unit 103, and wiring unit 105 on printed circuit board 104 are electrically connected with each other through a bonding wire 107. Furthermore, these element storage units 103 are sealed by a resin sealing member 108 in such a manner as to cover all light emitting device 106 and bonding wire 107. Patent Document 1 describes that, with this structure, it is possible to provide a light emitting device that improves the heat radiating property and is capable of effectively taking out light to the outside from the light emitting diode chip.
However, in light emitting device 101 shown in FIG. 14, printed circuit board 104, with wiring unit 105 made of copper foil being formed thereon, is disposed in the immediate vicinity of metal plate 102 made of aluminum (in the Figure, a linear distance d with respect to the horizontal direction is shown as a distance between metal plate 102 and wiring unit 105). For this reason, the resulting assumption is that sufficient electrical insulation is not achieved between metal plate 102 and wiring unit 105. Moreover, since light emitting device 101 as shown in FIG. 14 has printed circuit board 104 formed of a glass epoxy substrate, complicated manufacturing processes are required, thereby failing to provide a light emitting device at a low cost.
For example, Japanese Patent Laying-Open No. 2006-287020 (Patent Document 2) discloses a LED member 201 as schematically shown in FIG. 15. LED member 201 shown in FIG. 15 has a structure in which a heat radiating plate 203 made of metal or ceramics, with a LED chip 204 being mounted thereon, is joined in a through hole formed in a wiring board 202. In the example shown in FIG. 15, LED chip 204 and a wiring pattern 205 formed in wiring board 202 are electrically connected with each other by a bonding wire W, and these LED chip 204 and bonding wire W are embedded with a resin sealing member 206 made of a transparent resin. Patent Document 2 describes that, with this structure, the heat generation of the LED chip is effectively released, so that it becomes possible to provide a surface-packaging type LED member with good productivity, and a method for manufacturing the same.
In Patent Document 2, however, no detailed description is given as to the method for applying the transparent resin used for embedding LED chip 204 and bonding wire W. Moreover, in LED member 201 shown in FIG. 15 of Patent Document 2, since wiring pattern 205 is formed on side faces of wiring board 202 as well as on one portion of the back face, it is difficult to manufacture such a structure, resulting in a failure to manufacture the member at a low cost.